Field of the Invention
The invention relates to radiofrequency generation and more particularly to light modulated electron beam driven radiofrequency emission.
Various type of devices which generate radiofrequency power at wavelengths between about 10 and 200 centimeters (cm) are known. Those which utilize linear electron beams are divisible into 3 general types. The first type comprises devices employing longitudinal compression or bunching of the electron beam. The second type comprises devices utilizing radiofrequency deflection of an electron beam and the third type comprises devices utilizing a grid to vary the density of an electron beam.
Systems of the first type, such as the klystron and traveling wave tubes, employ beam velocity modulation. The overall length of the device must be proportional to the wavelength generated which means that these devices must be quite long and complex for wavelengths longer than 100 cm. Furthermore, the maximum ratio of radiofrequency power generated to direct current power consumed in such devices is approximately 0.7. It will be appreciated by those skilled in the art that a higher ratio is desirable for large high-power radiofrequency systems.
The devices of the second type, i.e., those using radiofrequency deflection of the electron beam such as the gyrocon, provide higher direct current to radiofrequency conversion efficiencies, on the order of 0.8. However, devices of this type in the 100-200 cm range are large, heavy and complex.
Devices in the third category, those utilizing a grid to vary the density of an electron beam, such as the triode and tetrode gridded electron tubes, provide only limited power from single devices. The overall direct current to radio-frequency conversion efficiency is lower than for the first two types of devices, 0.65 at best.
The present invention provides novel generation of large amounts of radiofrequency power in the 10-200 cm wavelength range in an inexpensive and compact apparatus that has high efficiency.